Hydroesterification of polymerized conjugated dienes

ABSTRACT

Polymerized 1,3-butadiene, including styrenic block copolymers, are functionalized with both carboxylic ester groups and ketone linking groups by reaction with carbon monoxide and an alcohol. Such conjugated diene polymers can be reacted in the presence of a catalyst composition that includes a cobalt compound and an amine ligand. The functionalized 1,3-butadiene polymers may be hydrogenated with a nickel/aluminum catalyst which removes olefinically unsaturated carbon-carbon bonds without substantially hydrogenating the ketone linking groups and carboxylic ester groups.

This is a division of application Ser. No. 07/357,451 filed May 26,1989.

BACKGROUND OF THE INVENTION

The invention relates to functionalized 1,3-butadiene polymers andcopolymers, and to specific processes for making functionalizedconjugated diene polymers.

The production of hydroxyl and carbonyl compounds by reacting olefinswith carbon monoxide and hydrogen is known. The products contain, as arule, one more carbon atom than the reacting olefin. The reactionrequires a hydrocarbon-soluble catalyst, usually one containing cobalt,iron, nickel or rhodium atoms, i.e., metals selected from Group 8 of thePeriodic Table of the Elements, in complex bond with at least one ligandconsisting of a carbon monoxide molecule and often a second ligandcontaining an organic compound of an atom, such as phosphorus orarsenic, selected from Group 5a of the Periodic Table.

U.S. Pat. No. 3,776,981 and equivalent British patent specification No.1,378,185 describe a process for preparing a hydroxylated blockcopolymer by reacting, with carbon monoxide and hydrogen, an unsaturatedblock copolymer having at least one polymer block of a monoalkenylareneand at least one polymer block of a conjugated diene wherein the polymerblock of the conjugated diene has a 1,2 or 3,4 microstructure content ofbetween 0% and 30% and a 1,4 microstructure content of between 100% and70%, the reaction with carbon monoxide and hydrogen being continueduntil substantially all of the unsaturation of the conjugated dieneblock(s) is removed, 10-100% thereof being replaced by hydroxymethylgroups and 90-0% thereof being replaced by hydrogen atoms. This knownprocess may be carried out as a one-step process, but then relativelyhigh hydrogen pressures are required.

European Patent Application Publication No. 148592 describes thepreparation of carboxylic acid or ester derivatives of polymericcompounds containing residual unsaturation. The polymers are reactedwith carbon monoxide and an alcohol in the presence of a protonic acid,a Group 8 metal or Group 8 metal compound, and a copper compound. Theapplication presents data for functionalization of polyisobutylene whichhas a single unsaturated carbon-carbon bond per molecule. Thefunctionalization of other unsaturated polymers by the same process issuggested although not specifically described.

U.S. Pat. No. 3,539,654 describes the modification of styrenic blockcopolymers with carbon monoxide and an acid in the presence a metalhalide catalyst. The resulting polymer was reported to have asignificant gel content and to contain ester and aldehyde functionalitybefore treatment with alcohol potash and with copper ions and water.This patent also describes the non-catalyzed reaction of a randomstructured polybutadiene with carbon monoxide in water followed byreaction with ethanol resulting in a polymer that reportedly containsether bonds or carboxylate groups.

Conversion of conjugated diene monomers into a polydiene block occurs inseveral ways using the lithium based catalysts, preferably lithiumalkyls, employed according to the prior art. Polymerization of butadieneleads to a mixture of several types of polymer microstructures, known ascis-1,4, trans-1,4 and 1,2 microstructures. In the cis-1,4 and trans-1,4structures, carbon arrangement is all in a line and no small side chainsare formed; thus, the double bonds produced are internal in the backbonechain. In the 1,2 microstructure, a two-carbon vinyl group is present asa short side chain directly attached to the two remaining carbon atomsof the original diene monomer unit. All three types of microstructuremay be present in a polydiene block, but process conditions are known inthe art to maximize or minimize any of the three types ofmicrostructures if so desired.

A fourth type of microstructure known as 3,4 microstructure is alsoformed when substituted conjugated diolefins are polymerized. This isthe case when isoprene is used.

SUMMARY OF THE INVENTION

Polymerized conjugated dienes having small molecule functional groupshave been prepared in a single step using carbon monoxide of arelatively low pressure.

The process of the invention includes reacting polymerized conjugateddienes, which includes styrenic block copolymers, with carbon monoxideand an alcohol in the presence of a cobalt compound and an amine ligand.

The polymers of the invention can be identified as 1,3-butadienepolymers or block copolymers having functionalized, polymerizedbutadiene units represented by both Equation I and Equation II: ##STR1##which the --CH═CH₂ pendent vinyl groups represent the 1,2 microstructureof the polymerized butadiene units, the --CH═CH-- internal unsaturationrepresents the 1,4 microstructure of the polymerized butadiene units,and R represents a hydrocarbon group having 1 to 20 carbon atoms.According to equation I, a carboxylic ester is formed. In equation II aketone linking group is formed which probably links a polymerizedbutadiene unit having 1,4 microstructure, with or without olefinicunsaturation, and an adjacent polymerized butadiene having 1,2microstructure, but may link different polymer molecules.

The reactions represented by equations I and II can occur at differentrates with equation I generally being dominant. However, the relativereaction rates are observed to vary depending on the relative amounts of1,2 and 1,4 microstructure and on the specific alcohol selected for thereaction.

The polymers of the invention which contain significant amounts of thefollowing structure: ##STR2## degrade in air under normal conditions. Asan alternative to the addition of stabilizers, hydrogenation of thesefunctionalized polymers with a nickel/aluminum catalyst significantlyimproves the polymer stability by removing the olefinic unsaturationwithout substantial hydrogenation of the ketone or ester groups.

The polymers of the invention were originally conceived as beingprepared with a catalyst composition that included the cobalt compounds.Production of the polymers with catalysts containing other metalcompounds such as palladium compounds is possible as demonstrated inU.S. patent application No. 255,232 filed Oct. 11, 1988. now U.S. Pat.No. 4,927,892.

DETAILED DESCRIPTION OF THE INVENTION

The polymers of the invention can be identified as 1,3-butadienepolymers or block copolymers having functionalized, polymerizedbutadiene units represented by both Equation I and Equation II: ##STR3##in which the --CH═CH₂ pendent vinyl groups represent the 1,2microstructure of the polymerized butadiene units, the --CH═CH--olefinic unsaturation represents the 1,4 microstructure of thepolymerized butadiene units, and R represents a hydrocarbon group having1 to 20 carbon atoms. According to Equation I, a carboxylic ester isformed. In Equation II a ketone linking group is formed which probablylinks a polymerized butadiene unit having 1,4 microstructure, with orwithout olefinic unsaturation, and an adjacent polymerized butadienehaving 1,2 microstructure, but may link different polymer molecules. Thereactions represented by equations I and II can occur at different rateswith equation I generally being dominant. However, the relative reactionrates are observed to vary depending on the relative amounts of 1,2 and1,4 microstructure and on the specific alcohol selected for thereaction.

The process of the invention includes reacting polymerized conjugateddienes, which includes styrenic block copolymers, with carbon monoxideand an alcohol, in the presence of a cobalt compound and an amineligand.

The starting polymer is preferably a block copolymer of 1,3-butadieneand a monoalkenylarene, the block copolymer having at least onemonoalkenylarene block and at least one polymerized 1,3-butadiene blockwhich includes adjacent 1,2 and 1,4 microstructure. Examples of usefulmonoalkenylarene compounds are styrene, 2-methylstyrene, and4-methylstyrene. Examples of other conjugated dienes which may bepresent in the block copolymer include isoprene and 1,3-pentadiene. Theblock copolymers may include random or tapered blocks as long as atleast one of the blocks contains predominently monoalkenylarene unitsand at least one of the polymer blocks contains at least predominentlyconjugated diene units. Very good results have been obtained withessentially homopolymer blocks of styrene and butadiene. When thecontent of aromatic vinyl compound in the block copolymer is small, theblock copolymer is a so-called thermoplastic rubber. Block copolymerswith a high aromatic vinyl compound content, such as more than 70% byweight, provide a resin. Many processes are known for the preparation ofblock copolymers, for example from U.S. Pat. No. 3,639,517.

The reactions represented by Equation I have been acheived withhomopolymer blocks of polymerized isoprene. However, the presence ofadjacent 1,4 and 1,2 microstructures in the isoprene blocks does notgive ketone linking groups as measured by infrared analysis. On theother hand, homopolymer blocks of polymerized butadiene having 10% ofthe butadiene units with the 1,4 microstructure were functionalized togive significant amounts of the ketone linking groups. Further,homopolymer blocks of butadiene having 90% of the butadiene units withthe 1,4 microstructure were functionalized to give more ketone linkinggroups than ester groups which represented about a ten-fold increase inthe amount of ketone linking groups in comparison to the functionalizedblocks having 10% of the butadiene units with the 1,4 microstructure.

Preferred block copolymers which may be used as precursers for thepolymers of the present invention are described in U.S. Pat. No. Re.27,145 as styrenic block copolymers having a general structure

    A--B--A

wherein the two terminal polymer blocks A comprise thermoplastic polymerblocks of the monoalkenylarenes, while block B is a conjugated dieneblock that contains polymerized butadiene units with both the 1,2 and1,4 microstructures prior to hydrogenation. The proportion of the blocksA to the block B and the relative molecular weights of each of theseblocks is balanced to obtain a rubber having an optimum combination ofproperties such that it behaves as a vulcanized rubber without requiringthe actual step of vulcanization. Although hydrogenation may be effectedselectively as disclosed in U.S. Pat. No. Re. 27,145, the selectivelyhydrogenated A--B--A block copolymers are deficient in many applicationsin which adhesion is required due to its hydrocarbon nature. Examplesinclude the toughening and compatibilization of polar polymers such asthe engineering thermoplastics, the adhesion to high energy substratesof hydrogenated block copolymer elastomer based adhesives, sealants andcoatings, and the use of hydrogenated elastomer in reinforced polymersystems. However, the placement onto the A--B--A block copolymer offunctional groups prior to hydrogenation in agreement with the presentinvention, which groups can provide interactions not possible withhydrocarbon polymers, solves the adhesion problem and extends the rangeof applicability of this material.

The molecular weight of the conjugated diene polymer is not critical andmay vary within wide ranges, for example between 2,000 and 1,000,000. Inview of the theoretical equations presented above, it is believed thatsubstantial presence of the ketone linking groups in the functionalizedpolymers depends on the presence in the butadiene polymer molecule ofadjacent butadiene units having 1,2 and 1,4 microstructures asrepresented by the following theoretical equation: ##STR4##

After the reaction is initiated by addition of the carbon monoxide tothe 1,2 microstructure, the adjacent 1,4 microstructure appears tocompete with the alcohol for formation of either a ketone linking group(Eq. III) or a carboxylic ester group (Eq. I). As shown in Equation II,the olefinic unsaturation in the polymer backbone in Equation III may beremoved during the one-step functionalization. Saturation of theseolefinic sites may involve capture of the metal catalyst and hydrogenfollowed by replacement of the metal with hydrogen during polymerworkup.

The alcohols used in making the polymers of the present invention may bealiphatic, cycloaliphatic or aromatic and may be substituted with one ormore substituents, for example with halogen atoms or cyano, ester,alkoxy, carboxyl or aryl groups. The alcohol may therefore be a phenol.Experiments conducted with methanol and with cyclohexanol indicate thatthe ratio of ketone linking groups to carboxylic ester groups formed ina given block copolymer depends on the selection of the alcohol. As muchas a three-fold decrease in the ratio of ketone linking groups to estergroups has been realized by changing the alcohol from cyclohexanol tomethanol. Other suitable alcohols are believed to include ethanol,propanol, 2-propanol, isobutanol, tert.-butyl alcohol, n-hexanol,2-ethylhexanol, stearyl alcohol, benzyl alcohol, chlorocapryl alcohol,ethylene glycol, 1,2-propanediol, 1,4-butanediol, glycerol, polyethyleneglycol, 1,6-hexanediol, phenol and cresol. The alcohol may also be ahydroxyl terminated ethoxylate or other long chain alcohol. If thealcohol has more than one hydroxyl group per molecule, a mono-ester maybe formed.

The precurser polymers and alcohol are reacted with carbon monoxidewhich may be pure or diluted with an inert gas, such as nitrogen, anoble gas or carbon dioxide. The carbon monoxide may also be produced inthe reaction mixture on a small scale as known in the art. Generally thepresence of more than 10% by volume of hydrogen is undesirable, sinceunder the reaction conditions it may cause hydrogenation ofethylenically unsaturated carbon carbon bonds. Preference is given tothe use of carbon monoxide or a carbon monoxide containing gas whichcontains less than 5% by volume of hydrogen.

The process of the present invention will usually be conducted in thepresence of a solvent for the precurser polymer. Examples of suchsolvents are hydrocarbons such as cyclohexane, hexane, heptane, octane,benzene, toluene, the three xylenes, ethylbenzene and cumene; etherssuch as diethyl ether; and tetrahydrofuran (THF). Mixtures of thehydrocarbons and ethers may be used.

The process for making the polymers according to the present inventionmay be carried out batchwise, semi-continuously or continuously.Catalyst residues are preferably removed from the polymer by extractioninto an aqueous acid such as dilute hydrochloric acid or sulfuric acid.Alternatively, the functionalized polymer solution may be purified bychromatography on basic and neutral alumina. Elution of the polymersolution through a combination bed of basic and neutral alumina left thespent catalyst residues in the chromatography column. The catalystresidues have also been removed by coagulation of the polymer inisopropyl alcohol.

Although the process of the present invention may be conducted attemperatures and pressures which may vary within wide ranges, theprocess temperature is preferably in the range of from 50° C. to 200° C.and the overall pressure is preferably in the range of from 1 to 100bar.

The process of the present invention may be carried out using a molarratio of vinyl groups in the conjugated diene hydrocarbon to alcoholwhich is not critical and may vary within wide ranges. This molar ratiousually lies in the range of from 0.01 to 10.

The process of the present invention is conducted in the presence of acatalyst composition that includes a cobalt compound such as cobalt2-ethylhexanoate (sometimes known as cobalt octanoate), cobalt acetate,or cobalt carbonyl, and an amine ligand such as pyridine, alkylsubstituted pyridines, pyrazine, and n-methyl pyrrole. The quantity ofthe cobalt compound is not critical. Preference is given to the use ofquantities in the range of from 0.001 to 0.1 gram-atom cobalt per mol of1,2 microstructure in the polymerized conjugated diene.

The process of the present invention may be carried out using a ratio ofmoles of the amine ligand per gram-atom of cobalt which is not criticaland may vary within wide ranges. This ratio is preferably at least 0.1and in particular in the range of from 1 to 100, thus promoting highreaction rates.

The polymers of the invention can also be made according to theprocesses described in U.S. patent application No. 255,232 filed Oct.11, 1988. The use of a palladium catalyst simplifies analysis of theproducts since cobalt broadens the bandwidths recorded by nuclearmagnetic resonance equipment.

The polymers of the invention which contain significant amounts of thefollowing structure: ##STR5## degrade in air under normal conditions.The polymers may be stabilized with conventional stabilizers if exposureto oxygen is required. The addition of conventional hindered phenolicshas been found to improve the polymer stability. Preferably, as analternative to the addition of stabilizers, hydrogenation of thesefunctionalized polymers with a nickel/aluminum catalyst significantlyimproves the polymer stability by removing the olefinic unsaturation inthe polymer backbone without substantial hydrogenation of the ketone orester groups.

Derivatives of the ester groups in the described polymers can beprepared using standard reactions such as hydrolysis to acids or thecorresponding salts, amidation with amines, or transesterification toform different ester groups.

The following Examples further illustrate the invention using the fourstyrenic block copolymers identified in Table 1.

                  TABLE 1                                                         ______________________________________                                        Polymer                                                                       Desig- Polymer Type                                                           nation (Block Molecular Weight)                                                                        Comments                                             ______________________________________                                        A      S-B-S (8,900-37,900-9,700)                                                                      38% 1,2-microstructure                               A'     S-B-S (7,800-35,000-7,200)                                                                      39% 1,2-microstructure                               B      S-I-S (11,000-138,000-11,000)                                          C      S-I (39,000-68,000)                                                    ______________________________________                                         where S = polystyrene, B = polybutadiene, I = polyisoprene               

EXAMPLE 1

Ketone linking groups and carboxylic ester groups were introduced intothe butadiene block of Polymer A using the following procedure.

A 5% wt/wt solution of Polymer A (74 g) in a mixed cyclohexane (1200 g)and methanol (180 g) solvent was loaded into a 1 gal. autoclave. Acatalyst charge of cobalt (2⁺) octanoate in mineral spirits (12%Co(w/w), 9.91 g, 20 mmol) and pyridine (4.8 g, 61 mmol) was added as asolution in cyclohexane (16 g). The well stirred solution was sparged atroom temperature with carbon monoxide (900 psig, 1 min) to removegaseous impurities. The vessel was brought up to reaction pressure (750psig) by addition of carbon monoxide and sealed. The vessel was heatedto 150° C. After 3.5 hr. at these conditions, the reaction was allowedto cool (reaction mixture was allowed to stand overnight, although thesolution was at room temperature in about 6 hrs). An aliquot of theproduct solution was cast into a thin polymer film by evaporation of thesolvent. Analysis of the elastomeric film by an Infrared (IR) methodfound both ester and ketone functionality in the product. Esterfunctionality was characterized by a signal on 1740 cm⁻¹ and ketoneswere noted at 1700 cm⁻¹. A band at 1600 cm⁻¹ was attributed topolystyrene and was used as an internal reference signal. Theabsorbances (A) of these bands were measured using an integration methodand compared as follows: A.sub.(Ketone) /A.sub.(Ester) =0.40;A.sub.(Ketone) /A.sub.(Styrene) =0.45; A.sub.(Ester) /A.sub.(Styrene)=1.14. The remainder of the product solution was reserved forhydrogenation studies.

EXAMPLE 2

A repeat of the experiment of Example 1 using substrate A' gave aproduct having similar functionality. The infrared analysis foundA.sub.(Ketone) /A.sub.(Ester) =0.35, A.sub.(Ester) /A.sub.(Styrene)=1.72, and A.sub.(Ketone) /A.sub.(Styrene) =0.61. This product hadslightly more functionality than the product described in Example 1.

The product of Example 2 was purified using a chromatography technique.The reaction product solution was acidified (100 ml of 5% w/w conc. HClin isopropyl alcohol (IPA)) and passed through a column (1.4 in. dia.)of basic alumina (80 g, Woelm 200 mesh, Super I Activity) over neutralalumina (150 g, same grade). Coagulation in IPA afforded a white polymercrumb with low levels of catalyst residues as determined by elementalanalysis (Co-210 ppm, N-34 ppm). The combined chromatography-coagulationprocess was preferred for removal of catalyst residues from thefunctionalized polymer.

EXAMPLE 3

The procedure of Example 1 was modified by reducing both the catalystconcentration and the reaction time. For this experiment, the catalystconcentration, both cobalt octanoate and pyridine, was reduced 4-foldfrom that used for Example I ([Co]=810 ppm). For this experiment, the[Co]=210 ppm while keeping the Pyridine/Co ratio at 3/1 (mol/mol). Thereaction time was 1.5 hr.

Analysis of the product by IR found A.sub.(Ketone) /A.sub.(Ester) =0.52,A.sub.(Ester) /A.sub.(Styrene) =0.83, and A.sub.(Ketone)/A.sub.(Styrene) =0.43. This product contained a lower level offunctionality than had been observed in Examples 1 and 2. As suspected,the reduction of catalyst concentration and reaction time reduced thelevel of functionality in the product.

The product was purified using a liquid-liquid extraction technique. Thereaction product solution was contacted with an equal volume mixture ofaqueous H₂ SO₄ (0.5% w/w) containing IPA (10% w/w). The blend wasallowed to phase separate and the aqueous phase was discarded. Thepolymer solution was washed 3 more times and then an aliquot wascoagulated in IPA. The resulting white polymer crumb contained less than270 ppm of Co. The combined extraction coagulation method had removedmost of the catalyst residue.

The remainder of the purified reaction product was reserved forhydrogenation and saponification experiments.

EXAMPLE 4

The procedure of Example 1 was modified by reducing the catalystconcentration and increasing the reaction time. For this experiment, thecatalyst concentrations, both cobalt and pyridine, were reduced 2-foldfrom that used in Example 1 ([Co]=810 ppm). For this experiment, the[Co]=400 ppm while keeping the pyridine/Co ratio at 3/1 (mol/mol). Thereaction time was 24 hr.

Analysis of the product by IR found A.sub.(Ketone) /A.sub.(Ester) =0.39,A.sub.(Ester) /A.sub.(Styrene) =4.47, and A.sub.(Ketone)/A.sub.(Styrene) =1.76. Clearly, reaction for a longer time afforded amore highly functionalized product in spite of the reduced catalystconcentration.

The product was washed as described in Example 3. An aliquot of thesolution was evaporated to dryness. Elemental analysis of the residuefound 460 ppm Co and 470 ppm N. The extraction procedure had removedmost of the catalyst residues.

EXAMPLE 5

The procedure of Example 1 was modified to employ Polymer B and areduced catalyst concentration. For this experiment, Polymer B, an SISpolymer, was used instead of Polymer A. The catalyst charge was 1/2 thatused in Example 1 ([Co]=810 ppm). In this example, the [Co]=400 ppmwhile keeping the pyridine/cobalt ratio at 3/1 (mol/mol). The reactiontime was extended to 5 hrs.

Analysis of the product by IR found no ketone functionality withA.sub.(Ketone) /A.sub.(Ester) =0, A.sub.(Ester) /A.sub.(Styrene) =0.23,and A.sub.(Ketone) /A.sub.(Styrene) =0. Changing the diene segment ofthe block copolymer from butadiene to isoprene had a profound affectupon the mixture of functional species noted in the product. Theisoprene based polymer gave a product containing only esterfunctionality.

EXAMPLE 6

The procedure of Example 1 was modified to use Polymer C and a reducedcatalyst concentration. From this experiment, Polymer C, an SI polymer,was used instead of Polymer A. The catalyst charge was 1/4 that used inExample 1 ([Co]=810 ppm). In this example, the [Co]=220 ppm whilekeeping the pyridine/cobalt ratio at 3/1 (mol/mol).

Analysis of the product by IR found no ketone functionality withA.sub.(Ketone) /A.sub.(Ester) =0, A.sub.(Ketone) /A.sub.(Styrene) =0,and A.sub.(Ester) /A.sub.(Styrene) =0.17. As noted in Example 5, theisoprene based reactant gave a ketone-free product.

The reaction product solution was purified using the chromatographymethod noted in Example 2. An aliquot of the purified solution wascoagulated in IPA affording a white polymer crumb (Co=170 ppm, N=20ppm).

EXAMPLE 7

A hydrogenation catalyst was prepared under an inert atmosphere bycombining slowly with stirring nickel 2-ethyl hexanoate (17.75 g of 12%w/w suspension in mineral spirits) in dry cyclohexane (250 g) andtriethyl aluminum (TEA) (33.3 g of 25.3% w/w solution in cyclohexane).The reagents were added slowly to minimize the temperature increaseassociated with the exothermic reaction. The product solution containedaluminum/nickel at a ratio of 2.3/1 (mol/mol) and was used as made forhydrogenation experiments.

The functionalized, unsaturated polymer used in this study was aketone-ester modified analog of Polymer A'. It was characterized asfollows A.sub.(Ketone) /A.sub.(Ester) =0.20, A.sub.(Ketone)/A.sub.(Styrene) =0.31, and A.sub.(Ester) /A.sub.(Styrene) =1.61. Asolution of this polymer in cyclohexane (5% w/w polymer) washydrogenated in a 1 gal. autoclave using the Ni/Al catalyst solutiondescribed above. The solution was sparged with hydrogen to removeimpurities. The reactor vent was closed and the well stirred mixturebrought to 38° C. and 600 psi of hydrogen. The hydrogenation catalystwas added in three increments (40%, 40%, and 20%) to a final nickelconcentration of 250 ppm. After each aliquot of catalyst was added, thereaction temperature was allowed to stabilize (exotherm) before the nextincrement of catalyst was added. The reaction was maintained at 90° C.for 3 hrs. The hydrogenated product solution was washed repeatedly withequal volumes of aqueous H₂ SO₄ (1% w/w) to remove the spent catalyst.The purified polymer was isolated by coagulation in IPA.

Analysis of the white polymer crumb by ozonolysis found 96.7% of the C═Csites had been hydrogenated; the product was essentially completelysaturated. When the IR analysis of Example 1 was applied to thismaterial, there was some inconclusive evidence for partial reduction ofketone groups to hydroxyl groups but no evidence for reduction of estersites to hydroxyl groups considering that A.sub.(Ketone) /A.sub.(Ester)=0.07, A.sub.(Ketone) /A.sub.(Styrene) =0.14 and A.sub.(Ester)/A.sub.(Styrene) =2.1. The Ni/Al hydrogenation method gave a styrenicblock copolymer having principally ketone and ester sites in a saturatedbutadiene segment.

The starting, unsaturated, functionalized 1,3-butadiene block copolymerhad poor stability on exposure to air in comparison to the unsaturated,functionalized isoprene block copolymers. A sample of the starting1,3-butadiene block copolymer which had been exposed to the atmospherefor 48 hours could not be redissolved. The hydrogenated polymer of thepresent example was freely soluble in both cyclohexane andtetrahydrofuran (THF) when analyzed after 48 days of exposure to air.Hydrogenation had greatly enhanced the stability of this polymer toexposure to air.

EXAMPLE 8

An aliquot of the purified product solution from Example 3 wascoagulated in IPA. The freshly precipitated polymer (5.7 g) wasimmediately redissolved in anhydrous THF (94 g). Under an inertatmosphere, this solution was treated, with stirring, with asaponification reagent, potassium trimethylsilanoate (1.4 g, 90%technical grade Aldrich Chemical Co., 0.01 mol). After 22 hr., analiquot of the product was cast into a thin polymer film and analyzed byIR. The product was characterized by a loss in ester sites(substantialreduction in the band at 1740 cm⁻¹) and the formation of an acid salt,--CO₂ K (a new, broad signal located between 1550 and 1610 cm⁻¹). Thesaponification technique had afforded a styrenic block copolymer havingketone and acid salt functionality distributed in the butadiene block ofthe block copolymer.

The preceding examples are illustrative of preferred embodiments of theinvention and do not limit the following claims to the products orprocesses described therein.

What is claimed is:
 1. A process for functionalizing a polymerizedconjugated diene, the process comprising the steps of:contacting apolymerized conjugated diene with carbon monoxide and an alcohol in thepresence of a catalyst, the catalyst comprising an amine ligand and acobalt compound selected from cobalt 2-ethylhexanoate, cobalt acetate,and cobalt carbonyl; and recovering the polymerized conjugated dieneafter sufficient time for addition of carboxylic ester groups.
 2. Theprocess as claimed in claim 1 further comprising the step ofhydrogenating the polymerized conjugated diene after the contactingstep.
 3. The process as claimed in claim 1 in which the alcohol ismethanol.
 4. The process as claimed in claim 1 in which the polymerizedconjugated diene is a 1,3-butadiene block of apolystyrene-polybutadienepolystyrene block copolymer, the 1,3-butadieneblock having both 1,2 and 1,4 microstructure.
 5. The process as claimedin claim 4 wherein the polymerized 1,3-butadiene is hydrogenated with anickel/aluminum catalyst.
 6. The process as claimed in claim 4 in whichat least a portion of the 1,2 microstructure is adjacent to at least aportion of the 1,4 microstructure.
 7. The process as claimed in claim 4in which cobalt is present in the range of from 0.001 to 0.1 gram-atomcobalt per mol of 1,2 microstructure in the polymerized conjugateddiene, at least 0.1 mol of pyridine is present per gram-atom of cobalt,and at least 0.01 mol of the alcohol is present per mol of 1,2microstructure in the polymerized conjugated diene.